Methods and apparatus for repeated ischemic conditioning treatment of hypertension and other medical conditions

ABSTRACT

Methods for ischemic conditioning treatments of a chronic medical condition are provided. Baseline disease-related parameters of a patient with a chronic medical condition are measured. Ischemia is induced in the patient by occluding and releasing arterial flow in one or more extremities of the patient. Post-ischemia parameters in the patient are measured. The baseline and post-ischemia parameters are compared to provide an assessment of an ischemic conditioning treatment of a chronic medical condition. The repeated, scheduled delivery of ischemic conditioning provides a beneficial, therapeutic effect on the chronic medical condition. Also provided is a device for pulse oximetry during periods of absent or low pulsatile blood flow including an artificial pulse generator as well as the use of said device in assessment of ischemic conditioning.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 12/323,392filed Nov. 25, 2008 entitled “Methods and Apparatus for RepeatedIschemic Conditioning Treatment of Hypertension and Similar Conditions”which is incorporated by reference in its entirety herein. Thisapplication claims priority based on U.S. Provisional Application No.60/989,946 filed Nov. 25, 2007, the disclosure of which is incorporatedherein by reference in its entirety.

FIELD OF THE INVENTION

This invention relates to methods and apparatus for ischemicconditioning to prevent, reduce, and/or treat certain chronic medicalconditions, in particular, hypertension. Ischemic conditioning isimplemented using noninvasive or invasive arterial occlusion and skincompression, and combinations thereof. More specifically, this inventionrelates to the treatment of high blood pressure (hypertension) usingrepeated ischemic conditioning.

BACKGROUND OF THE INVENTION

Without limiting the scope of the invention, its background is describedin connection with treatment of hypertension and other chronic medicalconditions including but not limited to peripheral arterial disease(PAD), Raynaud's syndrome, coronary heart disease (CHD), coronary arterydisease (CAD), diabetes, pulmonary hypertension (PH), and connectivetissue disorders.

By definition, chronic conditions are present when there is a persistentor lasting medical problem. For example, hypertension is considered tobe present when there is persistent elevation of either systolic bloodpressure or diastolic blood pressure, or when a patient has been placedon antihypertensive medication because of persistently elevated bloodpressure (regardless of the current blood pressure level). The bloodpressure level correlates directly with the magnitude of risk forclinical sequelae such as premature death, stroke, myocardialinfarction, congestive heart failure, renal insufficiency, dementia, andperipheral vascular disease. As a result, numerous antihypertensivedrugs have been developed to treat elevated blood pressure. Well knownclasses of prevalent anti-hypertensives include Angiotensin-ConvertingEnzyme (ACE) Inhibitors, Alpha₁ Antagonists, Angiotensin II (AT₁)Receptor Antagonists, Blockers, Calcium Antagonists, Central AdrenergicInhibitors, Direct Vasodilators, and Diuretics.

Pharmacological blood pressure lowering reduces the risk of prematurecardiovascular morbid and fatal events as well as all-cause mortality.Antihypertensive drug therapy has also been shown to prevent the gradualprogression of mild hypertension to more severe elevations of bloodpressure. The prevalence of pressure-related target-organ damage (i.e.,elevated serum creatinine, left ventricular hypertrophy) is also greaterat higher blood pressure levels. Hypertensives (individuals with chronichypertension) with pressure-related target-organ damage manifest aseveral-fold higher risk for pressure-related clinical complications ata given blood pressure level compared to hypertensives with similarlevels of pressure without target-organ damage. Early treatment ofhypertension favorably impacts long-term clinical risk, in part, bypreventing the development of pressure-related target organ damage.However, hypertensive agents can cause hazardous side effects related tothe dosage of medicine, the dangers of a rapidly decreasing bloodpressure, and ischemic infarction of organ tissues (e.g. anginapectoris, myocardial infarction, transient ischemic attack, and stroke).

Similarly, other chronic conditions such as peripheral arterial diseaseand diabetes are also treated by pharmacological therapies. Severalother important therapeutic principles are considered in treatingpatients of chronic conditions. In most cases, there is minimal to novalue in rapid pharmacological control of a persistent or recurringcondition. Rather, the goal for the vast majority is to prescribe acombination of appropriate lifestyle modifications (e.g. weight loss,dietary restriction, and increased physical activity) plus the lowestdoses of drug(s) that allow for normalization over the long term.Further, many medications have dose-related side effects. Drugacquisition costs also usually increase at higher dose levels. Incertain instances, cost is a major barrier to patient compliance withprescribed drug therapies. However, even the other noninvasive lifestyleapproaches to chronic disease management can be tempered with sideeffects and ineffectiveness. For example, regular exercise is known tolower blood pressure in healthy individuals by inducing ischemia butalso is problematic because it causes an increase in heart rate that maynot be tolerated well by some individuals. Further, exercise, diet, andweight loss programs are all well known to suffer problems ofcompliance.

Accordingly, what are needed are further methods and apparatus for themanagement and treatment of chronic medical conditions, in particularhypertension, as well as methods and apparatus for applying ischemicconditioning to improved athletic performance.

BRIEF SUMMARY OF THE INVENTION

The present invention provides methods and apparatus for utilizing theprotective effects of repeated, noninvasive applications of ischemicconditioning to treat long term chronic health conditions. In oneembodiment of the invention, repeated ischemic conditioning is appliedto confer pharmacologic-like and exercise-like therapeutic effects byincreasing the vasodilative capacity of the vasculature in the limbs inorder to positively affect a vascular condition.

In one embodiment of the invention, the patient is treated forhypertension, peripheral arterial disease, Raynaud's syndrome, coronaryheart disease (CHD), coronary artery disease (CAD), heart failure,pulmonary hypertension (PH), diabetes, and/or connective tissuedisorders. In one embodiment of the invention the vascular condition isa starting vascular condition of an athlete and the program of ischemicconditioning is administered on a repeated, scheduled basis adapted toimproved endurance and athletic performance.

In one embodiment of the invention, treatment is effected usingtransient ischemia. In other embodiments, treatment is complementedusing heat, including, for example, photo thermal energy.

In one embodiment, conditioning is effected by transiently andrepeatedly administering the treatment to at least one limb, or partthereof, for treatment or prevention of hypertension. The ischemiaconditioning treatment in one embodiment is transiently and repeatedlyapplied according to a schedule that is tailored to the medical andpsychosocial needs of the individual patient. In accordance with oneembodiment, the program of ischemic conditioning includes at least 1cycle of from 1 to 20 minutes of occlusion on at least one extremity, atleast 2-4 times per week. In one embodiment, the program of ischemicconditioning includes at least 1 cycle of from about 2 to about 5minutes of occlusion. The program can be adapted to the patient bymonitoring the relationship between different administration protocolsand the blood pressure of the patient with a goal towards maximizing thelowering of blood pressure in the individual patient. In one version ofthe invention, the program of ischemic conditioning includes at least 2cycles of about 2 to about 5 minutes of occlusion followed by about 2 toabout 5 minutes of release of an extremity at least 2-4 times per week.

In one embodiment of the invention, the ischemic conditioning is appliedto one or more extremities using an external cuff system for arterialocclusion. Alternatively or in addition, the ischemic conditioning isapplied to one or more extremities using external pressure to the skinusing a pressurizable garment.

In other embodiments, the ischemic conditioning includes a measurementaspect comprising one or more of determining a DTM response and adetermination of blood oxygen saturation during ischemia usingartificial pulse together with oximetry to improve the ischemicconditioning treatments. The artificial pulse may be generated bymechanical actuation. In some version of the invention, the mechanicalactuation is effected by pulsating fluid pressure in a cuff to causemechanical disturbance of arterial blood, repetitive, externalelectromechanical actuation, or repetitive, self-induced physicalmotion. Alternatively or in addition, the artificial pulse may begenerated by external non-mechanical optical illumination utilized toimitate an absorption pattern of a pulsatile blood flow signal byoscillating an intensity of a light source of either a single ormultiple wave length. Assessment of the progress of the ischemicconditioning treatment may include measuring one or more baselinehemodynamic parameters of a patient, applying an ischemic conditioningtreatment in the patient by occluding and releasing arterial flow in oneor more extremities of the patient on a scheduled, repeated basis,measuring post-ischemia parameters in the patient, and comparing thebaseline and post-ischemia parameters to provide an assessment of theischemic conditioning treatment over time.

In one embodiment wherein the ischemia conditioning treatment includesinduced ischemia, the induced ischemia is sufficient to induce reactivehyperemia in the distal extremity including both hands, both feet, orboth hands and feet, and/or portions thereof. The method may becomplemented by instructing a schedule of hand and/or foot exercises tothe patient.

In one embodiment wherein the ischemia conditioning treatment includesinduced ischemia, continued monitoring by pulse oximetry of the inducedischemia, in the absence of pulsatile flow, is enabled by the creationof artificial pulsatile signals. The artificial pulsatile signals can begenerated by either external mechanical actuation that causesoscillatory displacement of blood or external non-mechanical opticalillumination.

In one embodiment of the invention, a synergistic combination ofphysical exercise and ischemic conditioning is provided for preventionand treatment of hypertension. In another embodiment, methods andapparatus for treatment of intermittent claudication (a symptom ofperipheral arterial disease) is provided using ischemic conditioning toincrease dilative capacity and metabolic efficiency of conditionedareas. As a consequence, patients with intermittent claudication areenabled to walk longer distances and/or suffer less pain when walkingthe same distance.

In one embodiment employing induced ischemia as a conditioningtreatment, the induced ischemia is transiently and repeatedly induced inat least one limb or portion thereof of a patient according to aschedule of vascular occlusions. Alternatively, or in addition to otherconditioning treatments, in one embodiment, heat sufficient to inducevasodilation is applied to at least one distal extremity of the patient.In other embodiments, pharmacotherapy is initiated in conjunction withischemic conditioning and/or heat treatments. The conditioningpharmacotherapy is effected by administration with one or more of thegroup of vasodilators, anti-oxidants, anti-inflammatory and anestheticcompounds and nitric oxide (NO) donors, precursors and agonists. In oneembodiment, the pharmacotherapy is administered systemically.

In one embodiment, an apparatus is provided for transiently inducingischemia in a peripheral vascular area of a patient, the apparatusincluding a plurality of releasable compressing elements, each adaptedto reduce or occlude flow of blood to at least a portion of an extremityof the patient. The releasable compressing elements may comprise bandsdimensioned to be tightened around at least one extremity such as an armand/or leg to occlude flow of blood to at least a portion of the handsand/or feet. Alternatively, the releasable compressing elements maycomprise inflatable compression suits, mittens, socks, stockings, glovesand/or full body suits.

In one embodiment of the invention, apparatus for transiently andrepeatedly inducing ischemia in a peripheral vascular area of a patientincludes use of a plurality of releasable bands, each adapted to occludeblood supply to at least a hand or foot of the patient when tightened orinflated. As used here, the term band includes cuffs such as inflatableblood pressure type cuffs. The apparatus may be manual in operation ormay be automated such as with a control device for controllingcompression and release of elements in accordance with a schedule. Inone embodiment the apparatus includes a programmable computer forinducing ischemia in accordance with a schedule. In one embodiment theapparatus further includes a pump in operable communication with thereleasable compressing elements, wherein the action of the pump resultsin tightening or inflation by filling of the releasable compressingelements. The apparatus may further include one or more heatingmechanisms for intermittent heating at least one hand or foot.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts several locations for placement of occlusive bands orcuffs for inducing transient intermittent ischemia.

FIG. 2 depicts a halter worn embodiment enabling the patient to wear oneor more occlusive cuffs together with a pump and controlling unit forscheduled inflation of the cuff(s).

FIG. 3 a depicts an occlusive arm band or cuff in which cuff inflationand deflation can be controlled by a device mounted externally on thecuff and includes a fingertip monitor of induced ischemia. FIG. 3 bdepicts a system for monitoring the induced ischemia by a fingertipprobe that transmits information to the cuff control device and includesa finger mounted artificial pulse generator and pulse oximetry detector.

FIG. 4 a depicts a conventional finger pulse oximeter and reflectanceoximeter sensor. FIG. 4 b depicts a method that involves using externaloptical illumination to imitate the absorption patterns of pulsatileblood. FIG. 4 c depicts an embodiment of the external illuminationsource that takes its input from an external physiological signaldetector such as the ECG device in FIG. 4 d. FIG. 4 e depicts andembodiment of the device that uses an external electromechanicalactuator to cause oscillatory displacement of blood in the underlyingblood vessels. These oscillations are detected by the SpO₂ sensor andreported during a low or no flow state.

BRIEF DESCRIPTION OF THE INVENTION

Disclosed herein is a novel method of conditioning the vasculature ofpatients in order to reduce the potential for complications that occurwith frequency as a consequence of chronic medical conditions,particularly hypertension, but also Raynaud's syndrome, coronary heartdisease (CHD), coronary artery disease (CAD), peripheral arterialdisease (PAD), diabetes, pulmonary hypertension (PH), and/or connectivetissue disorders. In one embodiment, treatment of these chronicconditions is provided by repeated treatment or conditioning by usingtransient ischemia or hypoxia in order to increase the vasodilativecapacity of the vasculature. In other embodiments, treatment is providedby application of heat at levels sufficient to induce peripheralvasodilatation and increase cardiac output and vasodilative capacity.Treatment may be augmented using pharmacologic interventions includingblood pressure lowering drugs. In effect, the methods and apparatus ofthe present invention emulate the positive effects of exercise on thevasculature in a population that has reduced capacity for exercise dueto their chronic disease status.

The invention relies, at least in part, on physiologic reactions toischemia. Brief periods of ischemia (a local shortage of oxygen-carryingblood supply) in biological tissue, render that tissue more resistant tosubsequent ischemic insults through several mechanisms including throughincreased vasodilative capacity. Ischemic conditioning exerts protectionand appears to be a ubiquitous endogenous protective mechanism at thecellular level that has been observed in the heart of humans and everyanimal species tested. This protection has also been seen in organs suchas the liver, kidney, gut, skeletal tissue, urinary bladder and brain.In fact, ischemic conditioning can have an effect on any proliferativetissue, e.g. skin, hair, and bone marrow.

The therapeutic and protective effects of ischemic conditioning may bemediated by signal transduction changes to tissues. With respect tocardiac tissue, the current paradigm suggests that nonlethal episodes ofpre-ischemia reduce the infarct size that results from subsequent totalblockage of arterial blood supply. Ischemic conditioning has been foundto lead to the release of certain substances, such as adenosine andbradykinin. These substances bind to their G-protein-coupled receptorsand activate kinase signal transduction cascades. These kinases convergeon the mitochondria, resulting in the opening of the ATP-dependentmitochondrial potassium channel. Reactive oxygen species are thenreleased. Thus, additional protective signaling kinases can beactivated, such as heat shock inducing protein kinase C.

Further, the signaling kinases mediate the transcription of protectivedistal mediators and effectors, such as inducible nitric oxide synthase,manganese superoxide dismutase, heat-stress proteins and cyclo-oxygenase2, which manifest 24-72 hours after infarction to provide lateprotection. Suggested mechanisms of how these signaling transductionpathways mediate protection, and ultimately reduce infarct size, includemaintenance of mitochondrial ATP generation, reduced mitochondrialcalcium accumulation, reduced generation of oxidative stress, attenuatedapoptotic signaling and inhibition of mitochondrial permeabilitytransition-pore (mPTP) opening. Alternative protective mechanisms ofischemic conditioning that are independent of signal transductionpathways, such as those mediated by antioxidant and anti-inflammatorymechanisms, may provide further protection.

Even further, formation of vascular collaterals is also induced byischemia and hypoxia of blood vessels. Vascular endothelial growthfactor (VEGF) production can be induced in cells that are not receivingenough oxygen. When a cell is deficient in oxygen, it produces thetranscription factor Hypoxia Inducible Factor (HIF). HIF stimulates therelease of VEGF among other functions including modulation oferythropoiesis. Circulating VEGF then binds to VEGF receptors onendothelial cells and triggers a tyrosine kinase pathway leading toangiogenesis.

Ischemic conditioning has been shown to produce tolerance to reperfusiondamage from subsequent ischemic damage. One physiologic reaction tolocal ischemia in normal individuals is reactive hyperemia to thepreviously ischemic tissue. Arterial occlusion results in lack of oxygen(hypoxia) as well as an increase in vasoactive metabolites (includingadenosine and prostaglandins) in the tissues downstream from theocclusion. Reduction in oxygen tension in the vascular smooth musclecells surrounding the arterioles causes relaxation and dilation of thearterioles and thereby decreases vascular resistance. When the occlusionis released, blood flow is normally elevated as a consequence of thereduced vascular resistance.

Perfusion of downstream tissues is further augmented by flow-mediateddilation (FMD) of larger conduit arteries, which acts to prolong theperiod of increased blood flow. As a consequence of the elevated bloodflow induced by reactive hyperemia, downstream conduit vessels undergoluminal shear stress. Endothelial cells lining the arteries aresensitive to shear stress and the stress induces in opening ofcalcium-activated potassium channels and hyperpolarization of theendothelial cells with resulting calcium entry into the endothelialcells, which then activates endothelial nitric oxide synthase (eNOS).Consequent nitric oxide (NO) elaboration results in vasodilation.Endothelium-derived hyperpolarizing factor (EDHF), which is synthesizedby cytochrome epoxygenases and acts through calcium-activated potassiumchannels, has also been implicated in flow-mediated dilation.Endothelium derived prostaglandins are also thought to be involved inflow-mediated dilation.

The therapeutic effects of conditioning are mediated by changes to thevasculature and/or the neurovasculature, as well as anti-inflammatoryeffects. Nitric oxide (NO) bioavailability may be improved locally.Nitric oxide (NO) has been shown to be involved in cutaneous activevasodilation induced by systemic application of heat on the basis thatlocal inhibition of NO synthase results in inhibition of cutaneous localperfusion while local perfusion of the NO donor, sodium nitroprusside,results in maximum local cutaneous perfusion. Similarly, it has beenfound that NO mediates vasodilatation in response to local applicationof heat. Conversely, local cooling induces cold-sensitive afferentnerves to activate sympathetic nerves to release norepinephrine, whichleads to local cutaneous vasoconstriction.

Ischemia Preconditioning (IPC) has been found to have remote andsystemic protective effects in both human and animal models. Transientlimb ischemia (3 cycles of ischemia induced by cuff inflation anddeflation) on a contralateral arm provides protection againstischemia-reperfusion (inflation of a 12-cm-wide blood pressure cuffaround the upper arm to a pressure of 200 mm Hg for 20 minutes) inducedendothelial dysfunction in humans and reduces the extent of myocardialinfarction in experimental animals (four cycles of 5 minutes occlusionfollowed by 5 minutes rest, immediately before occlusion of the leftanterior descending (LAD) artery). This phenomenon suggests thatischemic conditioning creates natural therapeutic substances that canhave desirable systemic effects.

Recent evidence in a skeletal muscle model has suggested that IPCresults in increased functional capillary density, prevention ofischemia/reperfusion induced increases in leukocyte rolling, adhesion,and migration, as well as up-regulation of expression of nNOS, iNOS, andeNOS mRNA in ischemia reperfusion injured tissue. Research has alsoshown that ischemic preconditioning can result in elevations of heatshock proteins, antioxidant enzymes, Mn-superoxide dismutase andglutathione peroxidase, all of which provide protection from freeradical damage.

Although originally described as conferring protection againstmyocardial damage, preconditioned tissues have been shown to result inischemia tolerance through reduced energy requirements, altered energymetabolism, better electrolyte homeostasis and genetic re-organization,as well as reperfusion tolerance due to less reactive oxygen species andactivated neutrophils released, reduced apoptosis and bettermicrocirculatory perfusion compared to non-preconditioned tissue.

As used herein the term “ischemia” means lowering of baseline blood flowto a tissue. The term “hypoxia” means lowering of arterial PO₂. Bothischemia and hypoxia in extremities can be induced by occluding theblood supply upstream of the extremity. By “extremity” it is meant thelimbs (arms and legs). By “distal extremity” it is meant the hands andfeet, including the digits of the hands and feet. By “regional or local”it is meant, administration to a defined area of the body as contrastedwith systemic administration. One embodiment of the present inventionemploys transient, intermittent ischemia to condition and improve thevasculature of the extremities.

As used herein the phrase “compounds that increase the bioavailabilityof nitric oxide (NO)” include NO precursors, NO donors and NO agonists.An example of a NO precursor is the essential amino acid substrateL-arginine from which NO is synthesized by the action of nitric oxidesynthase (NOS). NO donors, which generate NO via NOS independentprocesses, include both fast and slow release compounds that typicallyrelease NO by either oxidation or reduction. Certain of the NO donorcompounds such as nitroglycerin (an organic nitrate), which isenzymatically degraded to generate NO, have been utilized for over acentury. Examples of NO donors (sometimes alternatively referred to inart as NO agonists) include the organic nitrates (e.g. glyceryltrinitrate, isosorbide dinitrate), sodium nitroprusside (SNP),syndnonimines (e.g. molsidomine, SIN-1), S-nitrosothiols (e.g.s-nitrosoglutathione), NONOates (e.g. Spermine-NONOate, DETA-NONOate),and hybrid donors such as the nitroaspirins and nicorandil. Certainother compounds that are considered herein to fall within the definitionof compounds that increase the bioavailability of NO are compounds, andmetabolites thereof, that include nitric oxide chemical structures andare considered to be NO agonists such as for example minoxidil(3-hydroxy-2-imino-6-(1-piperidyl)pyrimidin-4-amine). Such compounds areconsidered herein to be NO agonists if their action is the same as NO,such as for example, in opening of membrane potassium channels.

Transient Ischemia for Protection Against Chronic Medical Conditions

In one embodiment of the present invention, intermittent transientischemia is induced in one or more limbs, or portions thereof, of apatient. The intermittent transient ischemia stimulates and conditionsthe downstream vasculature and thereby prevents or reduces symptoms ofthe chronic medical condition.

In accordance with the novel indication of the present invention, in oneembodiment the body's own adaptive responses to induced ischemia orhypoxia are harnessed to provide protection against chronic medicalconditions such as hypertension, Raynaud's syndrome, coronary heartdisease (CHD), coronary artery disease (CAD), peripheral arterialdisease, diabetes, pulmonary hypertension (PH), connective tissuedisorders, and other chronic diseases involving the vasculature. Inaccordance with the method disclosed herein, a scheduled series oftransient ischemic episodes is administered. The scheduled series oftransient ischemic episodes provide protection against the incidence andseverity of chronic medical conditions particularly by increasing thedilative capacity in the vasculature of the limbs. Additional beneficialeffects include one or more of: increased scavenging of free radicals,reduction in inflammation, and increased functional capillary density.

In one embodiment of the invention, transient ischemia is implemented bycuffs or straps (106) that are secured around one or more of the limbsof the patient, as depicted in FIG. 1. As shown in FIG. 1, the occlusivecuffs or straps can be placed over one or more locations for compressionsufficient to occlude blood flow to the hands and or feet. For example,for occlusion of blood supply to the hands, compression can be appliedto the upper arm over the brachial artery, the lower arm over the radialand ulnar arteries, or the wrist over the radial artery. For occlusionof blood supply to the feet, compression may be applied to the upper legover the femoral and deep femoral arteries, or to the lower leg over thetibial arteries. In one embodiment, the cuffs are inflatable andinflation results in sufficient pressure around the circumference of thelimb to result in occlusion of the arterial blood supply to the limb. Inone embodiment, ischemic conditioning can be administered with cuffs onboth arms and both legs.

The duration of ischemia varies by therapeutic targets, but is typicallyprovided for a period from about 1 to about 20 minutes, preferably fromabout 2 to about 5 minutes, followed by release of the occlusion.Occlusion and release (reactive hyperemia) procedures with differentocclusion times are implemented depending on individual tolerance andresponse to therapy as well as the planned treatment schedule such thata desired distal and or contralateral vascular/neuro/neurovascularfunction is obtained. Repeated cuff occlusion and release is tailored toimprove vasoreactivity (increasing the vasodilative capacity) includingby improving nitric oxide bioavailability (reducing destruction orincreasing production). This effect can be seen in the same distalextremity as the cuff inflation but is also expected to haveneurovascular mediated systemic vasodilation as well.

In one embodiment of the invention, a programmable cuff inflation anddeflation device is employed to provide intermittent scheduled transientischemia. The device can inflate one or more cuffs on one or more bodyparts at a time. The method induces reactive hyperemia and can mimic theeffects of local exercise. The larger the area of ischemia the higherthe hyperemia.

A portable form of the device is implemented for ambulatory use such asthe embodiment depicted in part in FIG. 2. In the embodiment depicted inFIG. 2, one or more occlusive cuffs (106) are in electrical connectionvia cable (110) with programmable monitor (102) which may be wornanywhere on the body, such as for example on a waist band as depicted.The inclusive cuff can be inflated by an electric pump associated withthe programmable monitor, which also can be adapted to record thepattern of occlusion. Alternatively, the cuff(s) can be manuallyinflated at intervals. In one embodiment, the cuff(s) are manuallyinflated in response to a signal given by a programmable monitor thatinstructs inflation and deflation of the inflatable cuff(s). In anotherembodiment, the monitor instructs manual tightening and loosening of oneor more straps in accordance with a programmed schedule.

The duration of ischemia may not have a linear relationship with theeffect. After 30 minutes the hyperemia plateaus and the biochemicalimprint changes. Desired therapeutic effects are more expected in thefirst 20 minutes after which the potential harm from the ischemia wouldhave to be weighed against benefits obtained by diminishing chroniccomplications. In an embodiment, by scheduling separate ischemicconditioning treatments apart from each other in a day (e.g. 3 times aday) can provide maximum therapeutic effect. In an embodiment,conducting ischemic conditioning treatments frequently over extendedperiods of time (e.g. a day, month, or year) can enhance therapeuticeffect. In an embodiment, adjustments to ischemic conditioning regimenscan be administered based on assessments of treatment resistance over aperiod of time and thereby customized to achieve optimal responsivenessin the individual patient. Longitudinal measurement of blood pressureprovides a measure of efficacy in the treatment of hypertension.

In one embodiment of the invention, vascular and/or neurovascular and/orperipheral nerve function is determined on a distal extremity to aid indiagnosis, determination of progression and/or management of medicalconditions as well as use in assessing the status of the preventive andremediative therapies disclosed herein. In one embodiment, vascularand/or neurovascular function is determined by measuring the vascular orneurovascular response induced by transient blood flow occlusion in thevasculature leading to a distal extremity Vascular or neurovascularreactivity can be monitored by any one of several methods that detectblood flow differences in response to transient blood flow occlusionincluding inherent skin temperature, clearance of induced skintemperature, tonometry, Doppler ultrasound, laser Doppler flowmetry(such as by a laser Doppler perfusion imaging (LDPI) instrument),plethysmography, iontoporesis, capillometry, and/or changes in magneticor electromagnetic properties of the tissue.

Inherent skin temperature means the unaltered temperature of the skin.This is in contrast to an induced skin temperature measurement whichmeasures perfusion by clearance or wash-out of heat induced on the skin.Various methods of recording of inherent skin temperature on a fingertip or palm distal to an occlusive cuff are disclosed in Naghavi et al.,U.S. application Ser. No. 11/563,676 and PCT/US2005/018437 (published asWO2005/118516) which are incorporated by reference herein. Thecombination of occlusive means and skin temperature monitoring fordetermination of vascular reactivity has been termed Digital TemperatureMonitoring (DTM) by certain of the present inventors. In one standardutilization, DTM employs a standard arm-cuff vascular reactivityprocedure, which includes a temporary occlusion of blood flow in thearm. During the cuff occlusion, the lack of blood flow (ischemia)elicits a microvascular dilative response (opening small vessels). Uponreleasing the cuff, blood flow rushes into the forearm and hand, notonly restoring baseline flow but also resulting in an overshoot(reactive hyperemia). This overshoot causes shear stress in the larger(conduit) arteries, which stimulates these arteries (macrovessels) todilate and accommodate the increased blood flow.

A sensitive fingertip temperature sensor monitors, records, and analyzesfingertip temperature during the above cuff occlusion and releaseprocedure. Temperature changes serve as a surrogate marker of blood flowchanges that result from vascular reactivity. In one embodiment of theDTM procedure, an automated procedure is initiated beginning with anautomated blood pressure measurement, followed by cuff occlusion of theright arm. During the cuff occlusion (2 to 5 minutes), fingertiptemperature in the right hand falls because of the absence of warmcirculating blood. Once the cuff is released, blood flow rushes into theforearm and hand, causing a temperature rebound (TR) in the fingertipwhich is directly proportional to the vascular reactivity. The higherthe temperature rebound (TR), the better the vascular reactivity.

FIGS. 2 and 3 a depict use of fingertip monitor (104) in conjunctionwith a blood flow occlusive device (106) located on an upper or lowerextremity. In the depicted embodiment of FIG. 3 a, the fingertip monitoris a DTM that monitors fingertip temperature in conjunction with inducedreactive hyperemia in order to provide a surrogate marker of vascularreactivity as a result of repeated ischemic conditioning. In thedepicted embodiment of FIG. 3 b, an artificial pulse generator (2) isincluded to provide an artificial pulse and fingertip monitor (104) is,or includes, a pulse oximeter. In one embodiment the pulse generator (2)effects mechanical actuation by pulsating fluid pressure in a cuff tocause mechanical disturbance of arterial blood. In other versions,repetitive, external electromechanical actuation provides the artificialpulse. In still other versions, the artificial pulse is generated byexternal non-mechanical optical illumination utilized to imitate theabsorption patterns of a pulsatile blood flow signal by oscillating theintensity of a light source of either a single or multiple wave length.The optional extremity mounted monitor (102) is adapted to display oneor more of program parameters, ambient temperature, blood pressure, DTMparameters of fingertip temperature over time, and pulse oximetry data.

In one embodiment, the method for monitoring the vascular orneurovascular response further includes simultaneously measuring andrecording additional physiologic parameters including pulse rate, bloodpressure, galvanic response, sweating, core temperature, and/or skintemperature on a thoracic or truncal (abdominal) part.

In one alternative embodiment, local ischemia of the superficial skinlayers is provided by an inflatable mitten, sock or glove that operatesto provide compression against the skin and thus restrict normal bloodflow to the superficial tissues. As with ischemia induced by blockage ofblood flow by compression over an artery such as by inflation of a bloodpressure cuff, the induction of superficial pressure can be implementedaccording to a schedule of transient induced pressure as the treatmentor conditioning requires. Several other embodiments for inflatablecompression are possible such as for example a full body suit that canbe used to provide ischemia to the superficial skin layers.

Prevention and Treatment of Hypertension

Chronic medical conditions have various degrees of severity in differentindividuals including periods of partial remission and recrudescence.However, because each condition cannot be predicted and has variationsfor different patients, the ischemic conditioning therapy of the presentinvention can be modified to suit the unique parameters for theparticular condition and patient. The present method of administeringone or more transient ischemic episodes to one or more limbs accordingto a schedule is neither dangerous nor expensive and may be readilyimplemented in every patient. In one embodiment, cuffs are placed onboth arms and legs for ischemic conditioning in the treatment ofhypertension. The device can be implemented for either in-patient or,preferably, outpatient treatment. The transient ischemic episodesprovide protection and treatment against chronic medical conditions byseveral mechanisms including without limitation: increased nitric oxidebioavailability, increased scavenging of free radicals and reduction ofinflammation. If administered in a series of episodes over asufficiently amount of time, the method is expected to increasevasodilative capacity including by increased arterial and smooth muscleflexibility, as well as increases in functional capillary density, andmay be further expected to hasten wound healing.

In an embodiment of the invention, a scheduled series of transientischemic episodes is applied as conditioning to prevent or managechronic hypertension. Of the numerous compounds that are releasedfollowing an ischemic episode as described herein, several are known tohave anti-hypertensive effects. For example, increases in nitric oxideand adenosine bioavailability are known to occur after an ischemicepisode. These compounds are frequently targeted by drug therapies andare well known to relax smooth muscle cells, decrease arterialstiffness, and improve hypertension over time.

In an embodiment, episodes of transient ischemic conditioning areemployed to improve monitoring of stages of hypertension by vascularreactivity measurements. For example, since healthy individuals areexpected to have an increase in vascular reactivity by vasodilation uponan ischemic episode, healthy patients can show a decrease in bloodpressure following ischemic conditioning. Hypertensive patients can beexpected to have limited vasodilation capacity and thus have unchangedor even increased blood pressure after an ischemic conditioningtreatment. In an embodiment, any vascular reactivity measurement that issuitable for the methods described herein can be used to determinestages of hypertension by ischemic conditioning. In an embodiment,utilizing ischemic conditioning to characterize stages of hypertensiondoes not significantly affect heart rate of the patient. This creates anadvantage over the increased heart rate problem faced by manyexercise-induced ischemic vascular reactivity measures such as treadmillstress testing. Thus, ischemic conditioning is able to simulate ischemiceffects of exercise but avoid associated problems.

In an embodiment, other chronic medical conditions can also benefit fromscheduled ischemic conditioning and the resulting increase in perfusion,relaxation of smooth muscle cells, vasodilation, and elaboration ofanti-inflammatory and anti-oxidant mediators. For example, microvasculardilative capacity is hindered and inflammation is increased in Raynaud'ssyndrome and several associated disorders such as scleroderma (acollagen-related immune disorder) and small vessel vasculitis (includingvasculitis associated with anti-neutrophil cytoplasmic antibodies, orANCAs). Further, diabetes, insulin resistance, high blood glucose, andseveral other metabolic disregulations are well known to exacerbateinflammation and oxidation. Even further, patients with chronic coronaryconditions that reduce ejection fractions and perfusion can benefit fromthe effects of ischemic conditioning. For example, chronic coronaryheart disease patients, heart failure (especially the more severelysymptomatic such as in Class III and IV patients), ischemic heart, andstable angina can exhibit chest pain upon exercise which limits thecapacity for physical conditions. However, these patients can receivesimilar benefits of exercise by episodes of ischemic conditioning.Physical conditioning the extent tolerable is expected to increase thebenefits of the ischemic conditioning provided herein.

In an embodiment, ischemic conditioning can allow for detection andmanagement of subclinical diabetic neuropathy. Comparing nerveconduction differences before and after an episode of ischemicconditioning can provide information about existence and amounts ofnerve damage due to diabetic microvascular injury. Any suitable nervefunction measurement, such as needle electromyography (EMG), can beused.

Intermittent Heating for Protection and Treatment

In an alternative embodiment, increased blood flow, enhanced metabolicactivity, and anti-oxidant capability is obtained by intermittentheating of the hands and/or feet, or digits thereof. Heat is employed toshift the sympathetic-parasympathetic balance, including through theinduced increase in local production of nitric oxide, in order to inducevasodilation and reduced resistance to peripheral blood flow.

In certain embodiments, the heat is provided by a wearable appliancethat includes a heating element, a heating controller connected to theheating element, and a source of power for the heating element. As usedherein, the term “wearable appliance” includes heatable inserts or padsthat are dimensioned for placement in desired anatomical locations,including stand-alone appliances, appliances disposed in garments, andappliances that are used in association with a garment. Appliances thatare used in association with a garment include appliances that are worninside and those that are worn outside of the garment. As used herein,the term “non-wearable” appliance includes fixtures and/or portabledevices that are not dimensioned to be attached or carried by anindividual during ambulation.

In certain embodiments, a wearable treatment appliance is provided thatis dimensioned to be worn as mittens, socks or booties, or gloves. Theheating applied must be of sufficient magnitude to cause vasodilation.The optimal site for heating, as well as the intensity and duration ofheating, can be readily determined for a given individual based onwhether or not the desired vasodilation is obtained.

In one embodiment, local administration of heat is chronic, regular orperiodic for a period prior to episodes of ischemic conditioning. Forexample, the individual patient may schedule a pattern of heating, suchas for limited periods 2-10 times a day for a period preceding eachround of ischemic conditioning. In another embodiment, heat isadministered to the future site for a period prior to ischemicconditioning. Depending on responses desired and obtained in theindividual patient, the intensity and duration of heat can be tuned foroptimal responses.

In one embodiment of the invention, the heating is provided by FarInfrared Radiation (FIR). FIR is centered around a wavelength of 100 μmon the electromagnetic spectrum. Commercially available versions of suchelements able to provide heat to subcutaneous tissue include, forexample, FIR Radiant Heating elements. (Challenge Carbon Technology Co.,Taiwan). Such elements are suited for FIR heated clothing due to theirflat form and foldable, durable and washable properties. The elements asprovided for use in clothing include lithium-ion batteries, temperaturecontroller and OCP (Over-Charge Protector) integrated in one controllerthat provides for rapid heat up according to set upper levels.

Combination Therapies

In one embodiment of the invention, at least one ischemic conditioningtreatment of induced ischemia or hypoxia and/or application of heat iscombined with pharmacotherapy including by administration of ananti-hypertensive agent, vasodilating agent, anti-oxidant, and/oranti-inflammatory agent. Multiple compounds are known in each of thesecategories. Existing vasodilators include for example hydralazine, ACEinhibitors (such as for example enalapril), alpha-beta blockers (such asfor example carvedilol), minoxidil, and calcium channel blockers (suchas for example nisoldipine, nifedipine, diltiazem and verapamil). Newvasodilators such as, for example, oxdralazine are being developed andmay be equally suitable. Pharmacotherapy includes agents that increasethe local bioavailability of NO. The pharmacotherapy can be administeredsystemically or locally, such as by iontophoresis.

In another embodiment, at least one ischemia conditioning treatment ofinduced ischemia or hypoxia, and/or application of heat, is combinedwith non-pharmacologic techniques for modulating the autonomic nervoussystem (ANS), mostly for regional and transient modulation based onanatomical reflex zones. These non-pharmacologic techniques may includenon-invasive electric, magnetic, or electromagnetic neuromodulatingdevices used to increase local ANS activity. In another embodiment,transient intermittent ischemia and or heating is combined with handexercises to increase demand and thereby improve nitric oxidebioavailability in the target areas.

Improving Metabolic Endurance and Athletic Performance

In one embodiment of the invention, metabolic endurance and athleticperformance can be improved by repeated, scheduled ischemic conditioningtreatments. Such treatments provide a natural stimulus for the metabolicmachinery (mitochondrial activity, intracellular genes, mRNA, proteins)of the ischemic tissue to better adapt itself to anaerobic conditions,such as those encountered during prolonged exercise and continuous,strenuous activity. Repeated ischemic conditioning treatments areexpected to induce metabolic changes and adaptation similar to thatinduced by exercise conditioning. Ischemic conditioning modulates thesupply component, whereas exercise conditioning modulates the demandcomponent. The intracellular metabolic machinery responds to the balancebetween supply and demand for oxygen and other required nutrients. Adecrease in supply (ischemia) or an increase in demand (exercise) willtrigger a similar response.

Artificial Pulse Oximetry

Pulse oximetry is a non-invasive method allowing the monitoring of theoxygenation of a patient's hemoglobin. A sensor is placed on a thin partof the patient's anatomy, usually a fingertip or earlobe, and a lightcontaining both red and infrared wavelengths is passed from one side tothe other. Changing absorbance of each of the two wavelengths ismeasured, allowing determination of the absorbances due to the pulsingblood. Based upon the ratio of changing absorbance of the red andinfrared light caused by the difference in color between oxygen-bound(bright red) and oxygen unbound (dark red or blue, in severe cases)blood hemoglobin, a measure of oxygenation (the percent of hemoglobinmolecules bound with oxygen molecules) can be made.

Existing methods of pulse oximetry require a naturally occurringpulsatile signal in order to function. Standard pulse oximetry will notfunction correctly in the absence of pulsatile blood flow or during lowperfusion states, such as during surgery, hypovolemic shock, cardiogenicshock, septic shock, etc.

In one embodiment of the invention, artificial pulse oximetry can beused to measure oxygen saturation of blood hemoglobin (% SpO₂) in theabsence of naturally occurring pulsatile blood flow (e.g., surgery withheart bypass pump, circulatory shock, occlusive arterial disorders,etc.) in humans and animals. Artificial pulses can simulate naturalpulsatile blood flow in order to enable pulse oximetry devices tocalculate arterial and capillary oxygen saturation. This method may alsouse physiological signals detected by devices such as electrocardiogramsto simulate the natural pulsatile rhythm.

In another embodiment, the artificial pulsatile signals are generated byeither external mechanical actuation that causes oscillatorydisplacement of blood or external non-mechanical optical illumination.Methods of generating an artificial pulsatile signal include, but arenot limited to, the following:

-   -   Pulsating fluid pressure in a cuff to cause mechanical        disturbance of arterial blood.    -   Repetitive, external electromechanical actuation    -   Repetitive, self-induced physical motion    -   Optical illumination to imitate the absorption patterns of a        pulsatile blood flow signal by oscillating the intensity of a        light source (single or multiple wave length)

FIG. 4 a depicts a conventional finger pulse oximeter (1) andreflectance oximeter (6) sensor. A finger cuff (2) is placed on theproximal section of the finger and its pressure is increased tosupra-systolic by monitoring when the pulse oximeter loses signal. Onceat this supra-systolic level, its pressure is oscillated via the fluidtube (5) to create an artificial flow in the distal portion of thefingertip. This flow is detected by the pulse oximeter and reported toan interpreting device (8) which displays the saturated oxygen during anoccluded or low flow state.

FIG. 4 b depicts a method that involves using external opticalillumination (7) to imitate the absorption patterns of pulsatile blood.The pulse oximeter sensor (6) is able to detect this pulsatilefluctuation in light intensity and report saturated oxygen in a low orno flow state. FIG. 4 c depicts an embodiment of the externalillumination source (7) that takes its input (8) from an externalphysiological signal detector such as the ECG device (9) in FIG. 4 d.The ECG electrodes (10) attain the patient's heart rate, for example,and send an output signal (12) to the light source or anyelectromechanical actuator. FIG. 4 e depicts and embodiment of thedevice that uses an external electromechanical actuator (11) to causeoscillatory displacement of blood in the underlying blood vessels. Theseoscillations are detected by the SpO₂ sensor (1) and reported during alow or no flow state.

In another embodiment, this method can also be used with existing pulseoximetry sensors during conditions of low pulse amplitude ornon-pulsatile flow by programming the device to initiate artificialpulsations whenever pulsatile blood flow is absent. The artificialpulsations will create an interpretable signal and allow the pulseoximetry device to continue to measure blood oxygen saturation.

Although particular embodiments of the present invention have been shownand described, it should be understood that the above discussion is notintended to limit the present invention to these embodiments. Oneskilled in the art will readily appreciate that various changes andmodifications may be made without departing from the spirit and scope ofthe present invention. Thus, the present invention is intended to coveralternatives, modifications, and equivalents that may fall within thespirit and scope of the present invention as defined by the claims.

1. A method for improving endurance and athletic performance byrepeated, scheduled ischemic conditioning treatments comprising bloodflow occlusion and reperfusion.
 2. The method of claim 1, wherein theprogram of ischemic conditioning comprises at least 2 cycles of fromabout 2 to about 15 minutes of occlusion on at least one extremityfollowed by reperfusion.
 3. The method of claim 2, wherein the programof ischemic conditioning comprises at least 2 cycles of from about 2 toabout 5 minutes of occlusion.
 4. The method of claim 2, wherein theprogram of ischemic conditioning comprises a plurality of cycles ofocclusion followed by reperfusion within 24 hours of an athletic event.5. The method of claim 1, wherein the ischemic conditioning is appliedto one or more extremities using an external cuff system for arterialocclusion.
 6. The method of claim 1 wherein the ischemic conditioningprogram is personalized based on monitoring the level of ischemia. 7.The method of claim 6 wherein the level of ischemia is measured using anartificial pulse oximeter.
 8. The method of claim 1, wherein theischemic conditioning is applied to one or more extremities usingexternal pressure using a pressurizable garment.
 9. The method of claim1 wherein ischemic conditioning treatments are provided during physicalactivity or exercise.
 10. A method for improving metabolic endurance andathletic performance by repeated ischemic conditioning treatmentscomprising: a) measuring one or more baseline hemodynamic parameters ofa subject, b) applying an ischemic treatment in the subject adapted toimprove endurance and athletic performance by occluding and releasingarterial flow in one or more extremities of the subject on a repeatedbasis, c) measuring post-ischemic parameters in the subject, and d)comparing the baseline and post-ischemia parameters to provide anassessment of the ischemic conditioning treatment over time.
 11. Themethod of claim 10, further comprising measuring blood oxygen saturationduring ischemia using an artificial pulse together with oximetry toimprove assessment of the ischemic conditioning treatments.
 12. Themethod of claim 11, wherein the artificial pulse is generated bymechanical actuation.
 13. The method of claim 12, wherein the mechanicalactuation is affected by pulsating fluid pressure in a cuff to causemechanical disturbance of arterial blood, repetitive, externalelectromechanical actuation, or repetitive, self-induced physicalmotion.
 14. The method of claim 11, wherein the artificial pulse isgenerated by external non-mechanical optical illumination utilized toimitate the absorption patterns of a pulsatile blood flow signal byoscillating the intensity of a light source of either a single ormultiple wave length.
 15. A metabolic endurance and athletic performanceimproving device comprising an external cuff system for arterialocclusion and reperfusion for repeated, ischemic conditioning treatmentsfor improved metabolic endurance and athletic performance.
 16. Thedevice of claim 15 further comprising a pulse oximeter.
 17. The deviceof claim 16 further comprising an artificial pulse generator wherein thepulse oximeter is adapted to measure blood oxygenation in an artificialpulse created by the artificial pulse generator.
 18. The device of claim15 wherein a drop in finger tip skin temperature is a marker ofischemia.